Babies’ breathing tubes were dislodged at an unusual rate during Lucy Letby’s placements at Liverpool Women’s Hospital, the public inquiry into her crimes has heard.

The Thirlwall Inquiry at Liverpool Town Hall has been hearing opening statements from lawyers representing the families of babies whom the former nurse was charged with attacking.

Letby’s criminal convictions all relate to her time working on the Neonatal Unit at the Countess of Chester Hospital between June 2015 and June 2016.

But after her trial last year Cheshire Police revealed it was investigating the time she spent on two placements in Liverpool in 2012 and 2015.

Richard Baker KC, representing the families of 12 babies, said that Liverpool Women’s Hospital had conducted its own audit into Letby’s time there.

He told the inquiry that some babies collapsed due to dislodgement of endotracheal [breathing] tubes.

“This is not something that is happening all the time”, he said.

“It is unusual, and you will hear that it occurs generally in less than 1% of shifts.”

The audit found that there were recorded incidents of the tubes being dislodged on 40% of the shifts Letby worked at Liverpool Womens’ Hospital.

Mr Baker said: “In light of what we know now, we might wonder why.”

Liverpool Women’s NHS Foundation Trust had previously confirmed it was working with Cheshire Police on the investigation into Letby’s time at the hospital.

Mr Baker told the inquiry that people who doubted her guilt “should be ashamed of themselves”.

“The families are in no doubt that Letby is guilty. The jury were in no doubt that she is guilty.

“This is being arrogantly ignored.”

Mr Baker said that society often “prefers monsters to look like monsters, adding: “It’s sometimes hard to accept that evil can be banal.. but we should not be so naïve.

“To be successful, a serial killer hides in plain sight.”

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Peter Skelton KC, who is also representing families, told inquiry chair Lady Justice Thirlwall that the Countess of Chester’s former chief executive, Tony Chambers, and medical director, Ian Harvey, “should have overseen investigations” into Letby when senior consultants raised concerns.

Instead, Mr Skelton said, those doctors “were met with the obdurately closed minds of their managers and senior managers”.

He told the inquiry there were “five basic failures” from the period when Letby began harming babies.

Firstly, the failure to conduct swift and careful investigations into each of the deaths was “major and catastrophic”, he said.

Following that, clusters of deaths and near-fatal collapses should have been immediately escalated to senior management – which did not happen – Mr Skelton said.

When investigations did happen, those overseeing them should have borne in mind that unexpected and unexplained deaths could have been criminal acts.

He highlighted the 1991 case of Beverely Allitt, and the 2011 case of Victorino Ochua, who both murdered patients at their respective hospitals – and suggested it was “difficult to understand” why parallels were not drawn with Letby.

The fourth failing, Mr Skelton told the inquiry, was the failure to tell the police and the coroner about their concerns at the outset.

Finally, he said it was “morally indefensible” for the hospital not to inform the families that the causes of their babies’ deaths were being investigated.

Letby, from Hereford, is serving 15 whole-life orders after she was convicted at Manchester Crown Court of murdering seven infants and attempting to murder seven others, with two attempts on one of her victims, between June 2015 and June 2016.

The inquiry continues.

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